(1) Field of the Invention
The present invention relates to a method of bonding firmly silicon ceramic members with each other.
(2) Description of the Prior Art
Silicon ceramics, such as silicon nitride, silicon carbide and the like, have excellent mechanical strength, heat resistance, thermal shock resistance and corrosion resistance, and are expected to be used as high-temperature materials, such as gas turbine parts, engine parts and the like. In general, ceramics are inferior in moldability and workability to metal material which is used as a material for gas turbine parts, engine parts and the like. Among ceramics, silicon ceramics are difficult to be molded and worked, because it is difficult to select proper additives for molding and working silicon ceramics without decreasing their inherent excellent properties. While, gas turbine parts, such as a rotor, nozzle and the like, and engine parts, such as a combustion chamber, cylinder and the like, have a three-dimensionally curved structure and a complicated shape. In order to produce those engine parts from silicon ceramics having poor moldability and workability, there is generally carried out a method, wherein previously molded and worked separate members are fitted to each other or bonded with each other, and the resulting assembly is formed into one integral body.
For example, as the method of producing a silicon ceramic rotor by bonding a silicon ceramic blade with a silicon ceramic disc, there have hitherto been known a method, wherein a reaction-sintered silicon nitride blade and a silicon nitride disc produced by a hot press method are formed into one integral body by a hot press method through silicon nitride powder interposed therebetween; and a method, wherein a reaction-sintered silicon nitride formed by a slip cast method is interposed between a reaction-sintered silicon nitride blade and a silicon nitride disc produced by a hot press method, the resulting assembly is nitrided, and then the blade and disc are bonded with each other so as to form one integral body by a hot press method.
However, these methods have the following drawbacks. Because, in these methods, both the silicon nitride members to be bonded must be formed into one integral body by a hot press method, and therefore a complicated apparatus is required, mass production of aimed product is difficult, bonded members deform easily, the product is poor in the dimensional accuracy, and the bonding layer of both the members has often insufficiently bonded portion, from which the products are apt to be broken during the test.